US3899386A - Method for controlling vacuum pan - Google Patents

Method for controlling vacuum pan Download PDF

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Publication number
US3899386A
US3899386A US319938A US31993872A US3899386A US 3899386 A US3899386 A US 3899386A US 319938 A US319938 A US 319938A US 31993872 A US31993872 A US 31993872A US 3899386 A US3899386 A US 3899386A
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US
United States
Prior art keywords
solution
controlling
massecuite
vacuum pan
value
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US319938A
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English (en)
Inventor
Shigeo Komiyama
Ichiro Matsubara
Masatake Shiraishi
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Hitachi Ltd
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Hitachi Ltd
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    • C—CHEMISTRY; METALLURGY
    • C13—SUGAR INDUSTRY
    • C13B—PRODUCTION OF SUCROSE; APPARATUS SPECIALLY ADAPTED THEREFOR
    • C13B30/00—Crystallisation; Crystallising apparatus; Separating crystals from mother liquors ; Evaporating or boiling sugar juice
    • C13B30/02—Crystallisation; Crystallising apparatus
    • C13B30/026—Discontinuous processes or apparatus therefor
    • C13B30/027—Discontinuous processes or apparatus therefor combined with measuring instruments for effecting control of the process
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B01D9/0022—Evaporation of components of the mixture to be separated by reducing pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0018—Evaporation of components of the mixture to be separated
    • B01D9/0031—Evaporation of components of the mixture to be separated by heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D9/00—Crystallisation
    • B01D9/0063—Control or regulation

Definitions

  • CRYSTAL DlAMETER( mm) MASSECUIT comewm m CRYSTAL INTERVAL(X'/
  • One object of the present invention is to provide a method for automatically operating the vacuum pan without the difficulties encountered by the conventional automatic operation.
  • Another object of the present invention is to provide a method for controlling the vacuum pan according to which crystal growth is stably performed without the formation of false grains and the resolution of crystals taking place after seeding.
  • An additional object of the present invention is to provide a method for controlling the vacuum pan according to which the stable range in crystal growth is enlarged.
  • a further object of the present invention is to provide a method for controlling the vacuum pan according to which crystals are stably grown even if there is a disturbance owing to, for example, a change in the sort of supplied solution.
  • the quantity of supply of the solution is controlled by a signal obtained by comparing the reference signal from a programmer with more than two independent signals representative of the level of the solution in the vacuum pan, the inter-crystal gap length (or crystal content or consistency) or the average diameter of crystals instead of the level.
  • the quantity of supply of the solution is controlled by comparing the reference signal with the preferentially selected one of the independent signals.
  • the supply of the solution is controlled on the basis of the preferentially selected one of the components (detecting signals) concerning the control of the supply.
  • the control is temporarily held when the deviation of any non-selected component from the reference signal exceeds a predetermined level and the supply is controlled on the basis of each selected component when the deviation of the selected component becomes equal to a predetermined level.
  • FIG. I is a block diagram of a system for controlling the vacuum pan, embodying the present invention.
  • FIG. 2 is a graphical representation of the variations with time of variables important in the process of crystal growth.
  • FIG. 1 parts within an enclosure 50.by the long-and-two-short-dash line is a means first proposed by the inventors claiming the patentability of this application and the other parts or elements are familiar to those skilled in the art. And the conventional vacuum pan was run according to the following steps of procedure.
  • an open valve 2 provided in a vacuum pan 1 in FIG. 1 is closed while the main vacuum valve 4 and the cooling-water valve 5 of a barometric condenser 6 communicating via a pipe 3 with the vacuum pan 1 are opened.
  • vapor in the vacuum pan 1 is conducted into the barometric condenser 6 and condensed there into water by means of cooling water.
  • the condensed water is evacuated and non-condensed vapor is ejected from the vacuum vessel by means of a vacuum pump (not shown). By this process the reduction of pressure in the vacuum pan 1 takes place.
  • the steam valve 10 of the heat exchanger 9 is opened so that the heating of the solution in the pan is initiated.
  • a supply valve through which additional sugar solution is supplied into the vacuum pan is so controlled as to maintain the surface of the solution at a constant level.
  • the inside of the pan 1 is kept at a pressure of 50 to 150 mmHg Abs and at temperatures from 50 to C.
  • the present invention can be applied to any one of the above described method.
  • valve 10 of the heat exchanger 9 is closed and the valve 2 is opened to reduce the pressure in the vacuum pan 1.
  • Discharge The discharge valve 14 of the vacuum pan 1 is opened and the massecuite is discharged to be treated by the next separation process.
  • the massecuite is then divided through centrifugal separation into crystals and molasses. Thereafter, the separated crystals are passed through a dryer and a cooler and stored in silos or sugar bins and the sugar is packed and sent to the market.
  • washing of the pan A washing steam valve 15 and a washing water valve 16 are opened and the inside of the vacuum pan 1 is cleaned with steam and hot water.
  • the vacuum pan 1 is prepared for the following boiling step.
  • Reference numeral 17 designates an orifice; 18 a pressure-difference detector to detect the pressures of steam before and after the orifice l8; 19 an arithmetic unit to measure the flow rate of steam on the basis of Bemoullis theorem in response to the output of the detector l8; and 20 a programmer for the quantity of steam flow.
  • a signal from the programmer 20 is applied through a selector 21 to a steam flow controller 22 and the aperture of the valve 10 is controlled in response to the deviation of the output of the arithmetic unit 19 from the reference signal of the programmer 20.
  • a pressure detector 23 measures the absolute pressure in the vacuum pan 1
  • a temperature measuring element 24 measures the boiling point of the sugar solution in the vacuum pan
  • a pressure-temperature transducer 25 obtains from the absolute pressure in the pan the corresponding temperature in accordance with the pressure-temperature characteristic of the solvent (water in this case).
  • a supersaturation detector 26 receives the outputs of the element 24 and the transducer 25 to obtain the degree of supersaturation.
  • a cooling water controller 27 receives the output signal of the pressure detector 23 to control the cooling water valve 5.
  • An electromagnetic flow meter 28 delivers an output proportional to the flow rate of sugar solution to be applied to an arithmetic unit 29, the output signal of which, representative of the flow rate of sugar solution, is applied to a sugar-solution supply controller 30.
  • the degree of supersaturation of the sugar solution in the vacuum pan at values of from 1.00 to 1.25, i.e. at a quasi-stable condition, during seeding, crystals can be stably grown from added nuclei.
  • the degree of supersaturation indicates the condition of the crystals growth during the time from the step of seeding to the middle point of the step of crystal growth.
  • the gaps between the crystals are not constant and 1. during seeding that quantity of sugar solution enough for the heat exchanger to be completely immersed in the solution which is needed in the step of condensation, determines the gap length.
  • the gap length is usually larger than in the end of the seeding step so that it must be gradually lessened to a required value.
  • FIG. 2 gives the summary of the foregoing consideration, which shows an optimal model of crystal growth.
  • the model has been obtained as follows. It has been proved that it simulates a practical process of sugar boiling with a high accuracy.
  • the crystal is a cube. And it follows that where Q is the total volume of the massecuite in the pan, N the number of the total crystals, a the length of each edge of each crystal, and g the inter-crystal gap length.
  • the ratio D of the net volume of the total crystals to the total volume is expressed by the formula d) u+g where D is the crystal content.
  • the crystal content cannot be determined by direct measurement but it is well known that it can be indirectly measured by means of a consistency meter. Namely, the consistency can be given by the expression ing quantities from the curves in FIG. 2 into the above mentioned formulae.
  • the crystal content as described above. is related to the inter-crystal gap length and can be controlled according to the gap length and the average size by directly measuring the gap using an industrial television system or pattern recognition system.
  • the average diameter of crystals and the crystal content are controlled with the level and the consistency of sugar solution in the vacuum pan. This will be explained by reference to FIG.
  • a level detector 31 for detecting the level of the sugar solution in the pan
  • a consistency meter 32 for obtaining the consistency of the solution from the output of the consistency meter 32
  • a programmer 34 for controlling the level of the solution
  • a programmer 35 for controlling the consistency of the solution.
  • the present invention has the following features, which were devised to increase the range of stability.
  • the vacuum pan forms a part of the mutually interrelated, complicated systems and therefore the control system is given priority.
  • the quantity of sugar solution supply is controlled by the programmer 34 related to the level of the solution in the vacuum pan and the level controller is actuated according to the deviation of the output of the level detector 31 from the ref erence signal from the programmer 34 to operate the sugarsolution supply controller 30 through the level controller.
  • the signal from the programmer 35 is selected by means of the selector 37 prior to the signal from the programmer 34 so as to control the quantity of supply of sugar solution.
  • the control of consistency consists of control to provide additional sugar solution successively, control to dilute the solution in the vacuum pan and control to continue boiling the solution with the program stopped for a moment.
  • FIG. 1 are further shown a supersaturation controller 38, a consistency controller 39 which delivers an output according to the deviation of the output of the transducer 33 from the output of the programmer 35, and a switch 40 selectively switched over when the consistency is a better indication of control than the degree of supersaturation after seeding.
  • the programmer 35 controls the hot water valve 13.
  • the progress of the program is temporarily interrupted.
  • the solution is supplied to the pan in accordance with the programmed value of the supersaturation or consistency.
  • the program of the level control program is resumed when the level of the massecuite is gradually restored and reaches the predetermined programmed value.
  • This method of control is especially effective in the case where the program of consistency control can no longer be continued since the concentration of the sugar solution to be supplied is too thick to render control of consistency prior to the control of the level of the solution.
  • control can be resumed when the condition suitable for consistency control is reached again by vaporizing the water of the solution with the level of the solution kept constant.
  • the present invention can be applied to such processes involving crystallization as the productions of some drugs and of sodium glutamate.
  • a method for controlling a vacuum pan according to which heat is exchanged between a heat exchanger and a massecuite to generate and grow crystals in the massecuite in a batch operation, the improvement comprising (a) measuring the inter-crystal gap length of the crystals grown in the solution and controlling the quantity of the supply of the solution on the basis of the measured inter-crystal gap length to effectively grow crystals, and (b) measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured inter-crystal gap length with a programmed value for the inter-crystal gap length provided by a first program, comparing the measured value of said other parameter with a programmed value for said other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling said supply quantity, and controlling said supply quantity on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.
  • a method for controlling a vacuum pan according to which heat is exchanged between a heat exchanger and a massecuite to generate and grow crystals in the massecuite in a bath operation, the improvement comprising (a) measuring the crystal content of the massecuite and controlling the supply quantity of the solution on the basis of the measured quantity to effectively grow crystals, and (b) measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured crystal content of the massecuite with a programmed value for the crystal content of the massecuite provided by a first program, comparing the measured value of said other parameter with a programmed value for said other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling said supply quantity, and controlling said supply quantity on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected program.
  • a method for controlling a vacuum pan according to which heat is exchanged between a heat exchanger and a massecuite to generate and grow crystals in the massecuite in a batch operation, the improvement comprising (a) measuring the consistency of the massecuite and controlling the supply quantity of the solution on the basis of the measured quantity to effectively grow crystals, and (b) measuring the value of at least one other parameter indicative of, the progress of the crystal growing process, comparing the measured consistency of the solution with'a programmed.
  • step (3) preferentially controlling the supply of raw solution and the supply of water to the vacuum pan by reference to the deviation between thedetected value of the consistency of the massecuite and a signal from the consistency control programmer, the preferential'control of step (3) being in preference to control by reference to the deviation of the detected value of the liquid level of the massecuite and the signal from the level control programmer, the preferential control of step (3 being automatically selected by means of a selector.
  • a method for controlling a vacuum pan in which heat is exchanged between a heat exchanger and a raw solution to generate and grow crystals therein comprising measuring the value of a first parameter indicative of the progress of the crystal growing process, comparing the measured value of the first parameter with a programmed value for the first parameter provided by a first program, measuring the value of at least one other parameter indicative of the progress of the crystal growing process, comparing the measured value of said other parameter with a programmed value for the other parameter provided by a second program, automatically preferentially selecting either said first program or said second program for controlling the supply of the solution fed to said vac uum pan, and controlling the supply of solution fed to said vacuum pan on the basis of the deviation of the measured value from the programmed value of the parameter corresponding to the selected'program.
  • a method for controlling the liquid level, the amount of solution feed and the amount of solvent feed in a batch process for generating and growing crystals in a vacuum pan comprising measuring the liquid level of the solution in said vacuum pan; comparing the measured liquid level with a programmed value for the liquid level provided by a level control programmer; measuring the value of at least one other parameter indica-- tive of the progress of the crystal growing process, comparing themeasured value of said other parameter with a programmed value for said other parameter provided by a second program, automatically preferentially selecting said second program for controlling the amount of solution and solvent fed to said vacuum pan after a predetermined time period or when the liquid level in the vacuum pan reaches a predetermined value, and controlling the amount of solution and the amount of solvent fed to said vacuum pan on the basis of the deviation of the measured value from the programmed value of said other parameter.

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  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystals, And After-Treatments Of Crystals (AREA)
US319938A 1971-12-29 1972-12-29 Method for controlling vacuum pan Expired - Lifetime US3899386A (en)

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JP307572A JPS535271B2 (enrdf_load_stackoverflow) 1971-12-29 1971-12-29

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Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4009045A (en) * 1976-04-21 1977-02-22 Godchaux-Henderson Sugar Co., Inc. Continuous crystallization process and apparatus
US4050953A (en) * 1975-06-24 1977-09-27 Hitachi, Ltd. Process for continuously producing sugar
US4056364A (en) * 1974-08-30 1977-11-01 Amstar Corporation Two stage continuous crystallization apparatus with controls
US4119436A (en) * 1977-05-23 1978-10-10 Buttes Gas & Oil Co. Sugar refining process
US4120745A (en) * 1975-09-01 1978-10-17 Csr Limited Semi-continuous vacuum pan system
US4155774A (en) * 1977-08-09 1979-05-22 Randolph Ellwood A Process for controlling the rate of growth of particulate masses
US4437934A (en) 1982-09-13 1984-03-20 Purdue Research Foundation Method for controlling consistency of tomato products
US4557799A (en) * 1982-09-13 1985-12-10 Purdue Research Foundation Tomato consistency control apparatus
US4676870A (en) * 1986-06-02 1987-06-30 Phillips Petroleum Company Automatic control of a multiple-effect evaporator
US4875940A (en) * 1984-04-19 1989-10-24 The Tongaat-Hulett Group Limited Massecuite supersaturation monitor
EP2778238A3 (en) * 2013-03-13 2015-02-18 Rockwell Automation Technologies, Inc. Sugar crystallization control system and method

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5341442A (en) * 1975-08-19 1978-04-14 Itochu Seito Kk Apparatus for controlling sugarrcrystallization in crystallizing evaporator

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1708940A (en) * 1924-08-15 1929-04-16 American Maize Prod Co Process of producing dextrose
US1835621A (en) * 1930-05-28 1931-12-08 Us Pipe & Foundry Company Vacuum pan
US1976361A (en) * 1930-07-19 1934-10-09 Int Patents Dev Co Manufacture of anhydrous dextrose
US2073825A (en) * 1934-09-05 1937-03-16 Cons Ashcroft Hancock Co Automatic temperature and pressure control system
US2576496A (en) * 1947-07-31 1951-11-27 Taylor Instrument Co Method for controlling multipleefect evaporators
US2749745A (en) * 1954-11-12 1956-06-12 Honeywell Regulator Co Measuring apparatus for the degree of supersaturation of solutions
US3035634A (en) * 1957-03-26 1962-05-22 Atomic Energy Authority Uk Evaporators
US3220883A (en) * 1962-10-01 1965-11-30 Bailey Meter Co Automatic sequential control system and method for sugar pan operation
US3595624A (en) * 1968-05-16 1971-07-27 Texas Gulf Sulphur Co Method and apparatus for washing crystallizers
US3680621A (en) * 1968-03-04 1972-08-01 Fives Lille Cail Crystallization installation with control system
US3706599A (en) * 1971-05-03 1972-12-19 Grace W R & Co Sugar drying method
US3725127A (en) * 1970-03-19 1973-04-03 Fives Lille Cail Method and system for controlling a crystallization installation

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1708940A (en) * 1924-08-15 1929-04-16 American Maize Prod Co Process of producing dextrose
US1835621A (en) * 1930-05-28 1931-12-08 Us Pipe & Foundry Company Vacuum pan
US1976361A (en) * 1930-07-19 1934-10-09 Int Patents Dev Co Manufacture of anhydrous dextrose
US2073825A (en) * 1934-09-05 1937-03-16 Cons Ashcroft Hancock Co Automatic temperature and pressure control system
US2576496A (en) * 1947-07-31 1951-11-27 Taylor Instrument Co Method for controlling multipleefect evaporators
US2749745A (en) * 1954-11-12 1956-06-12 Honeywell Regulator Co Measuring apparatus for the degree of supersaturation of solutions
US3035634A (en) * 1957-03-26 1962-05-22 Atomic Energy Authority Uk Evaporators
US3220883A (en) * 1962-10-01 1965-11-30 Bailey Meter Co Automatic sequential control system and method for sugar pan operation
US3680621A (en) * 1968-03-04 1972-08-01 Fives Lille Cail Crystallization installation with control system
US3595624A (en) * 1968-05-16 1971-07-27 Texas Gulf Sulphur Co Method and apparatus for washing crystallizers
US3725127A (en) * 1970-03-19 1973-04-03 Fives Lille Cail Method and system for controlling a crystallization installation
US3706599A (en) * 1971-05-03 1972-12-19 Grace W R & Co Sugar drying method

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4056364A (en) * 1974-08-30 1977-11-01 Amstar Corporation Two stage continuous crystallization apparatus with controls
US4050953A (en) * 1975-06-24 1977-09-27 Hitachi, Ltd. Process for continuously producing sugar
US4120745A (en) * 1975-09-01 1978-10-17 Csr Limited Semi-continuous vacuum pan system
US4009045A (en) * 1976-04-21 1977-02-22 Godchaux-Henderson Sugar Co., Inc. Continuous crystallization process and apparatus
US4119436A (en) * 1977-05-23 1978-10-10 Buttes Gas & Oil Co. Sugar refining process
US4155774A (en) * 1977-08-09 1979-05-22 Randolph Ellwood A Process for controlling the rate of growth of particulate masses
US4437934A (en) 1982-09-13 1984-03-20 Purdue Research Foundation Method for controlling consistency of tomato products
US4557799A (en) * 1982-09-13 1985-12-10 Purdue Research Foundation Tomato consistency control apparatus
US4875940A (en) * 1984-04-19 1989-10-24 The Tongaat-Hulett Group Limited Massecuite supersaturation monitor
US4676870A (en) * 1986-06-02 1987-06-30 Phillips Petroleum Company Automatic control of a multiple-effect evaporator
EP2778238A3 (en) * 2013-03-13 2015-02-18 Rockwell Automation Technologies, Inc. Sugar crystallization control system and method
US9309576B2 (en) 2013-03-13 2016-04-12 Rockwell Automation Technologies, Inc. Sugar crystallization control system and method

Also Published As

Publication number Publication date
JPS4872080A (enrdf_load_stackoverflow) 1973-09-28
JPS535271B2 (enrdf_load_stackoverflow) 1978-02-25

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